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Question 17 of 27

Q.(a) List out the ICN principles. OR

(b) Differentiate tropic and nastic movements.
Tamil Nadu DgeTamil Nadu HSC First Year (DGE) Board 2020Subjective· 5mImportance★★★★★
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The International Code of Nomenclature (ICN, for algae, fungi, and plants) sets out fixed rules — independence from other kingdoms' naming, type-based application, priority of publication, one correct name per taxon, and Latinisation — to ensure every plant species has a single, stable, universally usable scientific name.

(a) Principles of the ICN (International Code of Nomenclature for algae, fungi, and plants) — answering the primary part of this question:

  1. Independence of nomenclature: Botanical nomenclature (for plants, algae, fungi) is independent of zoological nomenclature (for animals) and bacteriological nomenclature (for bacteria). This means the same genus/species name could, in principle, be validly used in both botanical and zoological nomenclature without conflict, since each system operates under its own separate code.

  2. Nomenclatural types: The application of names of taxonomic groups is determined by means of nomenclatural types — a designated type specimen (e.g. a herbarium sheet) permanently fixes which organism a given name refers to, even if the taxonomic circumscription of the group later changes.

  3. Principle of priority: The correct name for a taxonomic group is based on priority of publication — the earliest validly published name (that follows all the rules of the Code) takes precedence over any later synonym for the same taxon.

  4. One correct name: Each taxonomic group, with a particular circumscription, position, and rank, can bear only ONE correct (valid) scientific name — the earliest one satisfying the rules — except in specifically defined exceptional cases (such as conserved names).

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